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Y2 RNU block > Development of Reproductive Tract > Flashcards

Development of Reproductive Tract Flashcards

1
Q

where does the urogenital tract originate from

A

INTERMEDIATE MESODERM

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2
Q

In humans, there are 3 sets of kidney structures during development, Name them.

A

PRONEPHROS – cervical region
MESONEPHROS – abdominal region
METANEPHROS – pelvic region (definitive kidney)

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3
Q

what order are the 3 sets of kidneys formed

A

They are formed in a cranial to caudal and chronological sequence

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4
Q

describe pronephros

A
  • Rudimentary and non functional
  • intermediate mesoderm clumps and you get 7-10 solid cell groups in the cervical region
  • Regresses (disappears) by week 4
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5
Q

where is the mesonephros derived from

A

Derived from intermediate mesoderm from the upper thoracic and upper lumbar segments

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6
Q

when do the first excretory tubules of the mesonephros first appear

A

Week 4 after regression of the pronephros

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7
Q

mesonephros contributes supporting cells to the _______ _______

A

Genital

ridge

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8
Q

what is the definitive kidney

A

METAnephros

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9
Q

when does the metanephros appear and when does it become functional

A

week 5

becomes functional at week 11

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10
Q

how does the metanephros develop

A

Pronephros- rudimentary and then disappears
Mesonephros- appears at week 4 after regression of pronephros
Metanephros- mesonephros disappears and metanephros appears at week 5

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11
Q

Metanephros is formed from 2 parts that are at the bottom of the developing mesoderm, what are they?

A

Ureteric bud and metanephric cap/mesenchyme

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12
Q

How does the metanephric cap/ mesenchyme form

A

Mesoderm around the ureteric bud becomes metanephric cap or metanephric mesenchyme

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13
Q

Ureteric bud is an outgrowth of ________

A

mesonephric duct

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14
Q

what is the function of the cloaca

A

Posterior orifice that serves as the only opening for the intestinal, reproductive and urinary tracts at early stages. Anything collected from the developing kidneys will drain through the cloaca.

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15
Q

definitive kidney/ Metanephros arises from 2 sources:
- Metanephric cap
- Ureteric duct
what do both of these structure provide

A

Metanephric mesoderm- Provides the excretory units

Ureteric duct- Collecting system

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16
Q

When is the fetus able to produce urine

A

Kidney becomes functional at week 11 or 12 so since then

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17
Q

Do nephrons form until birth?

A

yes

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18
Q

what is the cloaca BEFORE it was divided to become cloaca

A

hindgut (endodermal lining)

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19
Q

What divides the cloaca by fusion with cloaca membrane

A

Urogenital septum

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20
Q

What forms after division of the cloaca

A

ANTERIOR UROGENITAL SINUS

POSTERIOR RECTAL/ANAL CANAL- forms anal canal

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21
Q

when does cloacal division occur

A

week 4-7

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22
Q

what forms the bladder

A
  • From cranial parts of urogenital sinus (division of cloaca)- anterior urogenital sinus
  • EXCEPT, Trigone region comes from the mesonephric duct
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23
Q

What germ layer is the bladder lined with

24
Q

What happens in the indifferent stage

A

2 gonads form- neither ovaries or testes
2 pairs of genital ducts surrounding the gonads form
- The paramesonephric ducts (Mullerian) FEMALE (more lateral than males)
- The mesonephric (Wolffian) ducts MALE

see pics for understanding
BOTH DUCTS IN A FOETUS REGARDLESS OF SEX

25
when does the indifferent stage occur
weeks 5-6
26
What is the function of the mesonephric duct
Drain urine from the mesonephric kidney
27
How does the mesonephric (wolffian) duct play a huge role in the development of the male reproductive system
Under the influence of testosterone, duct forms the ductus deferens and ejaculatory duct, and also forms the epididymis when mesonephros vanishes
28
What happens to the mesonephric (wolffian) duct in the female
almost completely disappears, leave a few non functional remnants
29
How does the PARAmesonephric (mullerian) duct play a huge role in the development of the female reproductive system
- Ends of the ducts widen to form funnel shaped cranial ends which open into the peritoneal cavity and the ducts approach each other in the midline - Cranial portion forms the uterine tubes - Caudal portion fuse to form the uterovaginal primordium (To form Uterus and superior vagina)
30
What happens to the PARAmesonephric (mullerian) duct in the males
Degeneration of (paramesonephric) Mullerian ducts due to the action of anti-mullerian hormone (AMH).
31
What makes the anti-mullerian hormones
This is a protein made by the Sertoli cells of the testis
32
When does sex determination start
week 7
33
How do the gonads initially appear as
- Pair of longitudinal ridges (Urogenital or gonadal ridges) | - Also has a mesoderm structure – projecting into the coelomic cavity
34
Describe the journey of the Primordial Germ cells for gonadal development
- Primordial germ cells (arrive as a subset of epiblast cells)– move out of the yolk sac and into the gonadal ridge - Move to the genital/gonadal ridge via dorsal mesentery - -> Forms the primitive gonads
35
why do the primordial germ cells move out of the yolk sac
due to the constant signalling occurring in this stage for development of the nervous system. --> SO keeps the gonads undifferentiated.
36
What happens if the primordial germ cells dont arrive into the gonadal ridge by week 6
the ridges develop no further and the gonads do not develop
37
Primordial germ cells form in a “cord like” structure called the _______ ____ _____
primitive sex cords
38
what is the function of the SRY (Sex determining Region of Y chromosome)
if the embryo is male, the Y chromosome encoded this gene- SRY. This acts on the somatic cells of the developing gonads: - to carry out proliferation of the primitive sex cords
39
What happens to the primitive sex cords after proliferation?
- Cords become horseshoe shaped Primitive germ cells move into the somatic cells - Cords break up into tubules and results in differentiation of somatic cells
40
What happens after differentiation of somatic cells and when the dense connective tissue forms
- Leydig cells begin to produce testosterone - Sertoli cells produce anti-Mullerian hormone Dense connective tissue forms and separates the cord from the surface epithelium - Forms Tunica albuginea
41
Testis cords are solid till puberty, what happens to them after reaching puberty?
- Acquire a lumen forming the seminiferous tubules - Join with the rete testis - Join with efferent ductules - Rete testis and mesonephric duct link to form the epididymis and ductus deferens
42
What gene is known to be the 'ovary determining gene' in females
Wnt 4
43
What happens in FEMALES after the primordial germ cells reach the genital ridge
PGCs divide by mitosis → pool of oogonia - Oogonia enter meiotic arrest at 4th month of gestattion and become oocytes - oocytes become associated with follicular cells- primordial follicles
44
When does development of the external genitalia occur
week 3 after fertilisation
45
describe the development of the genital tubercle and function of genital tuebrcle
- a pair of cloacal folds develop around cloacal membrane - they join to form the genital tubercle at the CRANIAL end Genital tubercle- forms penis in males and clitoris in females
46
what happens to the cloacal folds in the caudal side
- urethral folds in front - forms labia minora in female - anal folds behind - genital swellings then appear on either side of the urethral folds to form scrotal swellings in male, labia majora in the female
47
how does the urethra form in males
From middle pelvic part of urogenital sinus - In males, androgens from fetal testis cause genital tubercle to elongate into phallus - phallus pulls urethral folds forward - they form lateral walls of urethral groove and close over urethral plate to form penile urethra
48
what is the terminal part of male urethra (external urethral meatus) formed from and why is it open
forms from the surface ectoderm | it is open for ejaculation and peeing
49
how does the prostate gland develop
develops as outgrowths from the prostatic urethra
50
how does the bulbourethral gland develop
develop as outgrowths from penile urethra
51
how does the upper part of vagina form
comes from paramesonephric duct
52
how does the lower part of vagina form
forms from two outgrowths from urogenital sinus called the sinovaginal bulbs, these bulbs fuse to form a vaginal plate, and hollows to form a cavity
53
what happens when there is a failure of fusion of uterus in females
DOUBLE UTERUS - bicornuate uterus – only upper body of uterus involved - bicornuate uterus with rudimentary horn
54
what is vaginal atresia
failed canalisation (no hollow tube)
55
how does absence of vagina and the uterus occur
- failure of sinovaginal bulbs | - formation of bulbs is normally induced by uterus so uterus is usually also absent
56
what is hypospadias and treatment
- Urethra opening is not at the end of the penis but opens on the underside of the penis - Affects 1:300 boys (common) and 70% of cases are mild - Surgical correction necessary to enable urination whilst standing, often at around 12 months of age- fine after that

Y2 RNU block (12 decks)

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